1. Field of the Invention
This invention relates generally to an annealing method for an amorphous magnetic alloy and more particularly is directed to an annealing method for improving the permeability of the amorphous magnetic alloy.
2. Description of the Prior Art
Magnetic characteristics required by a soft magnetic material core such as a magnetic transducer head and so on are not only high permeability in the frequency band to be used but also high saturation magnetic flux density, magnetostriction of approximately zero and so on. Co-Fe-Si-B-based material mainly containing Co is well known as the amorphous magnetic material which can satisfy such requirements. Also, it is well known that, if the alloy is kept at a temperature higher than Curie temperature and lower than crystallization temperature and then quenched, the permeability thereof can be improved more. On the other hand, it is possible that the total amount of (Co+Fe) of the Co-Fe-Si-B-based amorphous magnetic material as described above is increased, the saturation magnetic flux density thereof can be raised. However, as shown in FIG. 1, as the total amount of (Co+Fe) increases, the permeability of the amorphous magnetic material as made is low so that it is difficult to provide particularly a magnetic transducer head for recording and/or playback audio signal or the like amorphous magnetic material in practice. Hence, a method for improving the permeability thereof is required. However, since the crystallization temperature T.sub.x of the Co-Fe-Si-B-based amorphous magnetic material is lowered as the total amount of (Co+Fe) increases and is further lowered than the Curie temperature T.sub.c when the total amount of (Co+Fe) is about 78 atomic %, the annealing by quenching the material from an elevated temperature higher than the Curie temperature T.sub.c can not be used. Resultantly, the saturation magnetic flux density of the composition the permeability of which can be improved by the afore-described annealing method is approximately 9000 Gauss at maximum. Thus, it is impossible to provide such a magnetic transducer head which can sufficiently utilize the magnetic characteristics of a magnetic recording medium having high coercive force such as a metal or alloy magnetic tape.